Alkali metal alumino silicates, methods for their production and compositions thereof

ABSTRACT

The subject matter of the following specification concerns the production of finely divided materials useful as pigments, moisture conditioners, paper fillers, and in rubber reinforcement and the like. Considering present economics, perhaps the most practical embodiment of the subject matter employs the reaction of a soluble sodium silicate and aluminum sulfate in producing precipitates commonly known and identifiable as sodium alumino silicates, the precipitate being ultimately collected as a dried particulate material of sub-micron particle size. The disclosed process involves conducting this general type of reaction in the presence of calculated quantity of sodium sulfate from the outset of the reaction whereby economics are improved and highly refined modifications in the characteristic of the final materials become obtainable. The reaction may be varied according to several conditions, such as pH, temperature, concentration, manner of feeding materials and the like whereby to better adapt the new materials to highly specialized needs, such as in rubber compounding and paper production.

United States Patent Hackbarth et al.

[ *Jan. 8, 1974 ALKALI METAL ALUMINO SILICATES,

METHODS FOR THEIR PRODUCTION AND COMPOSITIONS THEREOF [75] Inventors:Lowell E. Hackbarth, Bel Air, Md.;

Joseph T. Crockett, Auburn, Ala.

[73] Assignee: J. M. Huber Corporation, Borger,

Tex,

[ Notice: The portion of the term of this patent subsequent to June 1,1988, has been disclaimed.

[22] Filed: July 20, 1972 21 Appl. No.: 273,673

Related US. Application Data [60] Division of Ser. No. 112,469, Feb. 3,1971, which is a continuation-in-part of Ser. No. 730,892, May 21, 1968,Pat. No. 3,582,379.

[52] 11.8. C1. 162/181 C, 106/288 B, 162/162 [51] Int. Cl D2lh 3/82 [58}Field of Search 162/181 C, 162; 106/288 B [56] References Cited UNlTEDSTATES PATENTS 3,582,379 6/1971 Hackbark et al 106/288 B 2,739,0733/1956 Bertorelli 106/288 B Primary ExaminerS. Leon Bashore AssistantExaminerWilliam F. Smith Atmrney-Harold H. Flanders [5 7] ABSTRACT Thesubject matter of the following specification concerns the production offinely divided materials useful as pigments, moisture conditioners,paper fillers, and in rubber reinforcement and the like. Consideringpresent economics, perhaps the most practical embodiment of the subjectmatter employs the reaction of a soluble sodium silicate and aluminumsulfate in producing precipitates commonly known and identifiable assodium alumino silicates, the precipitate being ultimately collected asa dried particulate material of sub-micron particle size. The disclosedprocess involves conducting this general type of reaction in thepresence of calculated quantity of sodium sulfate from the outsetof thereaction whereby economics are improved and highly refined modificationsin the characteristic of the final materials become obtainable. The

reaction may be varied according to several conditions, such as pH,temperature, concentration, manner of feeding materials and the likewhereby to better adapt the new materials to highly specialized needs,such as in rubber compounding and paper production.

1 Claim, No Drawings ALKALI METAL ALUMINO SILICATES, METHODS FOR THEIRPRODUCTION AND COMPOSITIONS THEREOF This is a division of applicationSer. No. 112,469, filed Feb. 3, 1971, which is a continuation-in-part ofapplication Ser. No. 730,892, filed May 21, 1968, now U.S. Pat. No.3,582,379.

BACKGROUND OF THE INVENTION This invention relates to the production offinely divided materials having a variety of uses such as pigments,moisture conditioners, etc., but which are especially useful as rubberreinforcing materials and in paper making. The pigments of the inventionare produced by the reaction of a water soluble alkali metal silicatewith water soluble aluminum salts of strong acids, preferably by thereaction of sodium silicates and aluminum sulfate, according to methodsgenerally related to those described in U.S. Pat. No. 2,739,073. Theproducts resulting from the process of this patent, as well as from thesimilar process of this invention, are, in the sodium form, sometimesdescribed as sodium silico aluminates, sodium alumino silicates,synthetic zeolites, mineral pigments and the like.

SUMMARY OF THE INVENTION Although the products of the present processare in general much the same in chemical content as those described inthe aforementioned patent, they are markedly different in their physicalnature and surface chemistry. in particular, it is concluded that theydiffer as regards to their particle size, the chemical nature of theparticle surfaces, and in the nature of the state of aggregation, whichcharacteristics are regarded as of primary interest in the rubberreinforcing class of synthetic silicas and silicates. While the productsobtainable according to the aforesaid patent have good utility in rubbercompounding and paper making, the markedly different products of thisinvention are found to be quite superior, at least insofar as at presenthas been demonstrated in actual practice. More specifically, the newproducts of the present invention are at least comparable in utility tothe present best known rubber filler materials, while also having othervaluable improved utility in paper production. Therefore, the newproducts herein, may be readily distinguished from those of the saidpatent on the basis of rubber suitability criteria alone, and perhapsbetter so on such basis since certain highly technical physicalproperties by which they may be distinguished are at least to someextent speculative. Moreover, the process involved herein issignificantly different.

In addition to their improved qualities, the new products are producibleat considerable economic advantages over prior similar materials.

As regards to the economic advantages, such are illustrated in relationto the type of products resulting from the process described in U.S.Pat. No. 2,848,346, which products are currently accepted as beinghighly suitable for rubber compounding. In fact these latter patentedproducts possess the very optimum properties according to currentstandards. As will be observed upon reference to this patent, productsare produced which are referred to ashydrated silicas, (pigments arehydrated) and such hydrated silicas are produced by a different method,namely, by reaction of dilute sodium silicates with dilute sulfuricacid. Although the products of this latter patent are presently moresuitable than those of the aforesaid U.S. Pat. No. 2,739,073 as regardsto rubber compounding in particular, various factors involved in theirproduction, including raw material costs, lead to higher product costs.The present invention provides end products which are at least equal invaluable properties to those of the latter patent while being obtainableaccording to the general and less costly process of the former patent.

A further improvement in the process of this invention arises inconnection with the: economics of sodium sulfate recovery, this saltbeing a by-product of the reaction. More specifically, the presentprocess involves the deliberate addition of sodium sulfate as a part ofthe reaction medium, as a result of which the sulfate wash liquorcontains a much higher concentration of sodium sulfate, i.e., thequantity added plus the amount normally produced in the reaction. Sincethe quantity of water used for washing the reaction products free of sodium sulfate is the same whether sodium sulfate is added or not, theresult is that the wash liquor contains a much higher concentration ofthis salt and is therefore more economical to recover. As will be seenhowever, the addition of sodium sulfate has significance other than thisadvantage.

Another advantage of the invention which flows directly from reactingthe materials from the inception of the reaction in the presence ofsodium sulfate is that the resulting product is more uniform throughouta particular batch. It appears that sodium sulfate has a pronouncedeffect upon the nature and size of the aggregate, the tendency beingtoward the formation of smaller aggregates, together with an increase insurface area and oil absorption properties. It is thought possible thatthis advantage is due basically to the more uniform chemical reactionconditions of the present process in contrast to prior processes. Thebasic reaction heretofore known produces sodium sulfate. As the reactionproceeds over a period of time, sodium sulfate, starting from zeroquantity, builds up to the total amount formed at the conclusion of thereaction. As will be recognized, therefore, the reaction environment isquite different at the beginning as compared with the environment afterseveral minutes, and it constantly changes until complete. By providinga substantial amount of sodium sulfate from the beginning, the effectsof this salt are present from the beginning so that a period of timedoes not exist when the effects are completely absent and there is noperiod of time when there is less than the optimum amount of the salt.The

optimum amount, as well as useful minimum amounts, are a contribution ofthis invention.

Prior to this invention, it wasnot thought that the reaction of sodiumsilicates with aluminum sulfate could be conducted in such a manner asto effect a truly significant change or changes in the nature of the endproducts, at least as regards to those characteristics important in theart of rubber reinforcing. Thus, the present invention, whichdemonstrates clearly to the contrary, involves a highly revealingdiscovery in the art of silica-type pigment production. As is becomingmore and moreapparent, the chemistry and the chemical nature of thesurface of the synthetic silicas and silicates is very complex indeed,and it appears that a considerable amount of additional insight remainsto be gained concerning them before they can be considered to besubstantially totally understood and evaluated. In the present instance,it is thought to be highly probable that the products obtained aretechnically rather differently structured chemicals from any heretoforeknown; yet demonstration of such fact, followed by the provision of aprecisely distinguishing definition, is at least very difficult withpresent day equipment.

As pointed out above, the products of this invention are similar tothose heretofore produced following the procedures described in U.S.Pat. No. 2,739,073. In general, these products are compositionsessentially consisting of alkali metal, aluminum and silicon oxides,obtained in extremely small particle sizes, as very fine precipitates,by suitable commingling and reacting together, at very lowconcentrations, dilute aqueous solutions of an alkali metal silicate anda water soluble aluminum salt such as aluminum sulfate, aluminumchloride, aluminum nitrate or ammonium alum. The precipitated pigmentparticles are substantially all less than one micron in diameter, andthey average less than one-half micron in diameter. In the main theparticles range from about 0.02 0.5 micron. Moreover, they arecharacterized by extraordinary brightness and by other qualities ashereinafter described which make them exceptionally valuable for uses ofthe nature indicated above.

One of the most important aspects of the present invention involves thediscovery that the basic reaction may be selectively directed to producespecialized forms of sodium silico aluminates. By specialized forms ismeant that the present invention permits one to tailor the end productaccording to the most desirable form for use in a particularenvironment. Thus, where a reinforcing material for use in rubber shoesoles, heels, and the like of the highest quality is desired, certainoverall conditions are found to respond to provide an optimum set ofperformance characteristics. The present invention provides suchproducts of highly improved character. Moreover, as is well known, therubber industry not only requires reinforcing materials having veryparticular performance characteristics, but also the economic aspects ofthe final rubber producing process must not be affected adversely by thematerials added. For example, one may be able to produce a pigmenthaving desired, very fine performance characteristics, but the overallcure time in the rubber process necessitated by such pigment may belonger than a similar pigment having somewhat less acceptableperformance characteristics. This heretofore to some extent has led tothe compromising of quality of the rubber product in view of theimportant economic time factor in the production process. The overallcure time is also of importance in other rubber applications, such as intire production. Accordingly, it is quite important to consider therubber reinforcing art with the entire requirements in mind.

The aspect of the present invention having to do more particularly withrubber reinforcement in the field of tires, involves severalcharacteristics similar to those required in the shoe field; but certainperformance characteristics are required in tires which differsignificantly. In other words, the most desirable tire pigment is notnecessarily equally suitable in the shoe art. The present inventionprovides reinforcing material for tires which are tailored tofulfillspecific needs and which are superior in performance.

Further, where the pigments are to be employed as fillers in papermaking, certain somewhat different characteristics are desirable.Although any of the pigments produced according to this invention may beemployed as paper fillers with advantages over previous fillers, thosethat are produced under certain controlled conditions are moreespecially desirable because of greater improvement in strike-throughperformance. This is especially important in low grade paper stock, suchas newsprint.

Still further, the pigments produced according to this invention may beemployed in the fine paper as paper fillers with certain advantages overprevious fillers, some of which are imparting to fine paper a brightnessthat is at least 0.7 points higher and an opacity that is at least 0.5points higher than the brightness and opacity values imparted by thesodium alumino silicate produced according to methods generallydescribed in U.S. Pat. No. 2,739,073.

As indicated above, it is not believed that heretofore it has beenpossible to control the basic reaction in a consistent way such as toeffect these relatively delicate modifications of the end productscorresponding to improvements for particular uses.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Although the process of thisinvention involves a number of conditions which are varied according toparticular needs, it has been discovered that a predetermined minimumquantity of sodium sulfate must be present as a part of the reactionmedium from the inception of the reaction; otherwise, the end productsfail to acquire the physical and surface chemical characteristicsfalling within the range of pigments which are considered to be ofimproved nature herein, i.e., an improvement in at least one attribute.(At this point, it may be well to remark that if the general type ofreaction is conducted with a different aluminum salt, for example,aluminum chloride, then the corresponding acid salt is required, that isto say, with aluminum chloride one should employ sodium chloride in thereaction.) Continuing, although the sodium sulfate must be present fromthe beginning of the reaction in a minimum amount, it may be present inquite a large quantity without deleterious effects, at least insofar asthe objects of this invention are concerned. The present inventionteaches a range of sodium sulfate conditions which produces worthwhileresults. It is recognized that if sodium sulfate is present in anunnecessarily large quantity, a reversionary condition sets in and theadvantages otherwise produced according to this invention tend to becomelost. The exact point of this occurrence is exceedingly difficult todefine; and insofar as the point is established quantitatively in thisinvention, it should be understood that it is established in relation tothe performance qualities presently required in the various use areas,and not that a different quantity may produce improved productsconforming to a changed standard. As those required performancecharacteristics may alter in the future, it is foreseen that a greateror an even lesser quantity of sodium sulfate may be tolerable. It is,therefore, desired to emphasize that the discovery of advantageousresponsiveness of the basic reaction to sodium sulfate content inrelation to a community of productsis an extremely important, if not themost important aspect of the present invention. If the sodium sulfateconditions as taught herein are observed in conducting the reaction, animproved product results in at least one important respect which iscommon to the needs of the rubber industry in the overall and at thesame time the pigment has general utility as heretofore known andimproved utility in paper making; moreover, the economics of sodiumsulfate recovery are afforded.

The aspects of the process within the broad inventive concept as abovedescribed which are desirable to be managed for the purpose of producingstill other improved characteristics of the end products in relation tospecial needs are several in number. For example, in order to produce apigment having properties more suitable for the shoe industry, it isgenerally more advantageous to perform the reaction by delivering adilute stream of aluminum sulfate to a pre-established highly dilutesodium silicate sodium sulfate solution. Thus, the entirety of thesodium silicate and sodium sulfate calculated to be desirablequantity-wise in relation to the aluminum sulfate constitutes a reactionmedium to which the aluminum sulfate is fed over a given period of time.As will be more fully described herein after, the rate of feed of thealuminum sulfate provides a further means of control upon the nature ofthe end product. Still further as regards products having specialutility in the shoe industry, such products may be obtained by varyingthe approach to the reaction somewhat from that which has just beendescribed. More particularly, it is found that the reaction may beconducted with the view to obtaining such improved prod ucts varyingonly slightly in character by establishing a sodium silicate-sodiumsulfate reaction medium composed of as little as approximately 50percent of the total of such materials calculated to be necessary in thereaction in relation to the aluminum sulfate, the remainder of thesodium silicate sodium sulfate solution being fed to the reaction massas a stream (or streams) concurrently with a separate stream of aluminumsulfate. Here again, some variation of the rate of feed of aluminumsulfate and other process modifications are possible within limitswithout destruction of desirable qualities of the end product. Forexample, by feeding a stream of water soluble aluminum salt, moreparticularly aluminum sulfate, to the reaction medium for at least tenseconds or more in time in excess of the ordinary time generallyincluded within the normal procedure for adding aluminum sulfate to thereaction prior to adding the other reactant, sodium silicate describedin U.S. Pat. No. 2,739,073 and in co-pending application No. 730,892filed May 21, 1968, the resulting product consequently imparts to finepaper improvements in sheet brightness and opacity. Modification of theconditions just described, i.e., manner of commingling the reactants,leads to the production of slightly different products; however, all ofthe products are improved in one respect or another over thosepreviously known for use in the same environment.

Considering the process from a different standpoint, namely, thestandpoint of producing end products having qualities which areespecially desirable in the paper industry and tire field, preferablythe reaction is conducted in a slightly different manner since thedesired differences in the products are significant and demonstrable inuse. In this connection, and in contrast to the foregoing approach, itis desirable that the major portions of the reacting materials be fedconcurrently as separate streams to a highly dilute sodiumsilicatesodium sulfate reaction medium. More especially, a relativelysmaller portion of the pre-calculated amounts of sodium silicate andsodium sulfate (usually herein fed as a single combined stream) isemployed as the reaction medium, the remainder of such pre-calculatedamount constituting the sodium silicate-sodium sulfate feedstream, whichis fed simultaneously with a stream of aluminum sulfate. The propertiesthat are produced according to this technique are found to appearincreasingly prominently in relation to the smallness of the quantity ofsodium silicate-sodium sulfate in the so lution which provides thereaction medium. The critical point is in relation to the minimumquantity of sodium sulfate which is desirable to be present initially asa part of the reaction medium. Depending upon the concentration ofsodium sulfate in the precalculated feedstream, the exact amountdelivered to form the reaction medium will vary. However, for example,in performing the reaction within the preferred conditions herein,approximately 10 percent of the total quantity of silicate and sodiumsulfate are employed to constitute the reaction medium to which theremainder of the reactants are delivered over a period of time; and,while still obtaining a product of improved quality for the particularuse, as much as approximately 50 percent of the total sodiumsilicate-sodium sulfate pre calculated amount may be delivered to formthe reaction medium.

Thus, it will be observed that the characteristics of the reactionmedium as regards to the quantity of sodium silicate sodium sulfatecontent therein in relation to the remainder of the reactants to be fedis a significant variable in the tailoring of specific end products.

As a general proposition, once having determined the quantity of sodiumsulfate necessary in the production of a given quantity of end products,regardless of the character of the end productsspecifically sought, thepresence of more or less quantity of the total sodium sulfate in theinitial reaction batch is not found to be highly critical; but theminimum quantity of sodium sulfate is always provided at the outset ofthe reaction. Thus, the sodium sulfate-sodium silicate does notnecessarily require to be admixed and fed in as a single stream toprovide the reaction medium. Instead, the quantity of sodium sulfate maybe fed separately as a stream, or the total, or any part of the totalquantity thereof, may be pre-delivered to the water mass in advance ofdelivery of the reacting chemicals. Moreover, if desired, the sodiumsulfate may be fed to the reaction medium with the aluminum sulfate, aminimum quantity of the sodium sulfate having been pre-delivered to thereaction zone.

A further significant aspect of the process concerns the pH of the finalpigment end products. In this connection, pigments which are produced byconducting the process within the range of operating techniques abovedescribed, and which have improved properties over those heretoforeknown, have a pH value of from about 7 to 11. Moreover, it has beendiscovered as a further aspect of the invention that, within this range,pigment pl-l has a definite relation to the suitability of the pigmentsfor use in the several different environments generally discussed above.More particularly, it has been discovered that when a pigment isproduced having a pH within the range of about 7.2 to 8.5, moreespecially and preferably, within the range of about 7.5 to 8, suchpigments exhibit certain characteristics or properties rendering themmore useful in paper and in the production of rubber tires. Pigmentshaving a pH within the range of about 7 to 8 are found to exhibitcertain characteristics or properties rendering them of improvedusefulness in the shoe industry in the production of soles, heels andthe like. Therefore, looking to the object of providing the tailor-madeproducts of the present invention, it..is an .aspecto f the invention tocontrol the pH of the ultimate product.

pH control involves particular adjustment to the initial reactionleading to pigment precipitation. Basically, the reaction is conductedsuch that the final pigment slurry resulting from the reaction fallswithin particular levels according to the desired ultimate pH of thepigment. in the case of products especially useful in paper and also inreinforcing tire rubber, the reaction is controlled to provide a finalslurry pH falling between about 5.5 to 9.5, more particularly andpreferably a pH of about 5.8 to 7.0. In the case of pigment productionfor special utility in the shoe industry, the final slurry may fallwithin the same pH range, that is to say about 5.5 to 9.5, however, moreparticularly and preferably, the final slurry pH is controlled such thatits pH is about 5.8 to 6.0. As will be understood by those skilled inthe art, the final slurry pH is directly related to the sulfate ioncontent of the slurry and this is readily controlled by adjustment ofthe quantity of aluminum sulfate which is fed to the reaction. That isto say, since the pH of the final slurry is desired to fall on the acidside, then slightly more aluminum sulfate than needed is provided forreaction with the sodium silicate. Similarly, if a lower slurry pH isdesired, a slightly higher quantity of aluminum sulfate is provided. Itmay be remarked that the higher pH pigments are seen to afford slightlyshorter scorch times in the rubber compounding process. On the otherhand, as the pigment pH increases towards a higher value, the stiffnessquality of the rubber end product begins to degrade slightly.

As will be seen from the foregoing, the desired pigment product pH levelis very readily controlled or established by adjusting the reactionmedium to the acid side with a slight excess of aluminum sulfate. It isnow desired to discuss the matter of pH from another standpoint alsohaving a bearing on the nature of the end products. This additionalstandpoint has to do with the pH of the reaction medium over the periodof time during which the precipitation reaction is taking place. Thisperiod of time may be varied widely; however, in general, the reactionsextend from approximately 20 to approximately 40 minutes for completion,aside from ageing time before the slurry is filtered. Thus, indiscussing precipitation pH, it will be understood that such is inrelation to conditions occurring in such periods of time as well asother times which may be adopted for carrying out the precipitationreaction. As aforesaid, it is found that the precipitation pH levelexerts a marked effect upon the nature of the particles which make upthe final pigment end products. In the case of paper and tire pigments,it is found to be desirable to maintain precipitating pH from about 10.4to 10.9. in the case of products specialized for use in the shoeindustry, it has been found to be desirable to maintain a slightlyhigher pH, that is from about 10.9 to about 1 1.3, preferably about 11.2. It should be pointed out that precise pH values are difficult toobserve and maintain as a matter of certainty in a given reactionbecause the permissible deviation from the preferred precipitating pHvalues is within the limits of error of pH measuring instruments.Therefore, in the present process the reaction conditions are maintainedon the basis of pre-established feed rates of the aluminum sulfate. Aswould be understood, the higher the feed rate for aluminum sulfate, thelower the precipitation pH and vice versa. Of course, where all or amajor quantity of the sodium silicate is present in the reaction mediumfrom the outset of the reaction, alum feed rate has very little effecton pH until that quantity is used up in the reaction.

It is perhaps impossible to offer an unequivocal statement concerningthe physical or chemical modification which is brought about in theprecipitated particles as a result of pH control during theprecipitation reaction or as the pH of the ultimate pigment particles isdifferent. However, insofar as observations are believed to permit, itappears that precipitation pH values as indicated, especially thepreferred levels, lead to the production of more uniform pigmentparticles as regards to their size distribution, which uniformityappears to result by way of reduction of the number of coarser particlesin the mass. It appears that as the precipitation pH is lower there isproduced a larger number of relatively large agglomerated type ofpigment particles. Where the precipitation pH is higher, that is withinthe range preferred herein, the agglomerate structures are smaller;moreover, such pigments are found to have a higher surface area and theagglomerate is less dense.

As regards to the pH of the pigment particle, it is found that higher pHpigments tend to impart a relatively high level of stiffness to therubber products; and, whereas the opposite is true in pigments of lowerpH, the tear resistance of the rubber product is improved. Theseoccurrences are thought to be related to surface chemistrycharacteristics of the particles, considering such in relation toreactions occurring between the rubber and such pigment surfaces.Further discussion on this point at least at this time, is believed tobe entirely theoretical. It is the end result that is accomplished bypigments of the characteristics described herein which are important tonote in examining the matter from the standpoint of improved usefulness,the explanation as to why being in any event unnecessary.

As is well known, the general reaction involving sodium silicate andaluminum sulfate may be carried out over a wide temperature range. Thepresence of the minimum quantity of sodium sulfate throughout thereaction according to this invention requires no particular changes inestablished temperature conditions. According to this invention, theimproved characteristics of the pigments, which affect their increasedutility in the rubber compounding processes wherein the scorch time ismarkedly reduced, result where the reaction as heretofore described isconducted at a temperature within the range of about F to about 180F orhigher, although there is no particular advantage in higher reactiontemperatures. All things considered in rendering the reaction morepractical, a more suitable temperature range is from about 1 15F toabout F. Preferably, depending upon exactly how the proces is conducted,the volume and temperature of reaction medium initially established,whether it contain all of the sodium silicate-sodium sulfate solution oronly a portion thereof, the aluminum sulfate and sodium silicate streamsare adjusted to provide a reaction temperature falling within the rangeof about 125 to about 150, preferably about 130 to 140. in all cases,however, it has been found to be advantageous to feed the aluminumsulfate stream to the reaction at a temperature as high as this rangeand preferably at a temperature of at least 130 up to about 160Fdepending upon the objective. The importance of the aluminum sulfatetemperature control is thought to be related to modifications occurringin the surface chemistry of the particles of pigments produced.Specifically, certain of the properties of the pigments of the presentinvention are thought to occur according to the coordination of aluminum with silica, precipitation of the pigment during the reactionbeing achieved via aluminum sulfate. It is thought that suchprecipitation and coordination depend significantly upon the uniformavailability of aluminum ions in an acidic media. Such availabilityitself is related to the dissociation and acidity of the aluminumsulfate, which is temperature related. It may be, therefore, that therecommended temperature control of the aluminum sulfate feed streamleads to the production of pigments having a higher uniformity ofsurface chemistry characteristic, the reaction environment being such asto afford especially uniform precipitating and surface coordinatingconditions. It will be appreciated that such observations may or may notbe completely descriptive of circumstances, at least not entirely so,for the reason that a variety of other reaction conditions andrelationships are involved. Moreover, the matter of surface chemistrymust be regarded as at least somewhat speculative at this stage ofknowledge of the art, and especially so where the ultimate properties ofthe products herein produced are attributed to such phenomena.

Where the objective is to produce pigments intended for application inthe shoe industry, as in rubber soles, heels, etc., it has been found tobe more suitable and preferable to feed aluminum sulfate at atemperature nearer the upper end of this temperature range, moreparticularly, about 160F. The lower end of the temperature range, i.e.,about 130F to about 140F, has been found to be preferable in producingtire pigments and paper fillers. lnsofar as sodium silicate feedtemperature is concerned, this is not critical and it may be deliveredat room temperature up to the desired reaction temperature.

In practicing the invention, a sodium silicate-sodium sulfate solutionis prepared containing the silicate within the range of about 0.50 to3.0 lbs/gal and sodium sulfate is added thereto in an amount of from Ito percent by weight of such silicate solution. In general, it is foundto be advantageous to increase the sodium sulfate content as the sodiumsilicate solution is more dilute. Thus, if a relatively dilute sodiumsilicate solution is prepared, sodium sulfate is supplied in a greateramount, that is to say towards the upper part of the l to [0 percentrange. Conversely, more concentrated silicate solutions are combinedwith a lower quantity of sodium sulfate. Where the process is carriedout by feeding separate streams of the thus prepared sodiumsilicate-sodium sulfate solution and the aluminum sulfate solution, asis presently preferred in the production of tire pigments and newspaperpigments especially suitable concentrations for sodium silicate arefound to lie within the range of about 1.4 to 1.6 lbs/gal, usually about1.5 lbs/gal. For this particular sodium silicate concentration, theamount of sodium sulfate supplied is about 5 percent by weight of thesodium silicate solution. Such stream is delivered to a reaction chambercontaining a volume of fresh water, such volume being from about 0.4 toabout 1.2 gallons of water/lb. of silicate, preferably about 0.6 to 1.Where the objective is to produce pigments especially usable in the shoeindustry, in which case preferably the aluminum sulfate is fed directlyto the total quantity of sodium silicatesodium sulfate provided as afurther diluted reaction medium, the concentration of the preparedsodium silicate solution is preferably within the range of about 0.6 to0.8 lbs/gal, usually about 0.70 lbs/gal. Sodium sul fate in thisinstance is employed on the basis of about 3 percent by weight of thesilicate solution.

In the foregoing part of this specification it has been indicated thatthe approach to conducting the precipitation reaction having particularregard to the commin gling of the total quantities of the reactants issubject to a variety of approaches. More particularly, and somewhat insummary, it has been indicated that a reaction medium may be establishedcontaining from a very small quantity of each of sodium silicate andsodium sulfate up to the total calculated quantity of such materials towhich various reaction media aluminum sulfate is thereafter fed as asubstantially constant stream, the commingling taking place withthorough agitation. As will be appreciated, the total quantity of thereactants and the sodium sulfate can be commingled very rapidly or veryslowly and, in any case, the precipitation reaction will proceed. Thus,for example, if the object of bringing the reactants together is merelyto produce a sodium alumino silicate in the presence of the minimumquantity of sodium sulfate as herein taught, whereby to obtain a productwithout particular regard to performance characteristics in highlyspecialized applications, or particular applications not requiringnotice of rates of commingling of the reactants, it will be appreciatedthat one may disregard consideration of such rates. In general,according to this invention, or otherwise, however, it is not found tobe advantageous to entirely disregard rates of commingling because ofthe fact that uniformity of the particulate mass composing the endproducts is rendered poor or economics are adversely affected. Accordingto this invention it is not seen to be desirable in any instance toattempt to complete the reaction in a shorter period of time than about3 minutes regardless of the actual sodium silicate-sodium sulfatereaction medium that has been established, that is to say, the amount ofthe calculated quantity of such materials; provided as a dilute medium.Moreover, it may be mentioned that little or no advantage is gained byunduly prolonging the reaction, and therefore, in no instance is itfound to be essential to extend the commingling of the reactants beyonda period of about minutes, such times representing the feed time foraluminum sulfate, and also the sodium silicate-sodium sulfate solutionin those instances where their total quantities are not provided as thereaction medium for receiving the aluminum sulfate. Therefore, as apractical matter commingling of the reactants should take place withinthese extremes, i-.e., about 3 to 75 minutes. Usually, however, it isnot found to be especially suitable to approach either extreme tooclosely although, depending upon the object of the process, that is tosay which product is sought having particular high performancecharacteristics for specified application such as herein mentioned, itis found that the commingling rates are suitably respectively longer orshorter. A more suitable range for producing pigments of general utilityfrom the standpoint of particle uniformity in such things as particlesize, oil absorption and surface area is from about 10 to 50 minutes.More particularly, where the total or a major quantity of the calculatedamount of sodium silicate and sodium sulfate is provided as a reactionmedium, (such being the preferred approach in producing materials ofhigher usefulness in shoe soles and the like,) it is preferred todeliver the aluminum sulfate somewhat more rapidly, for example, withina period not greater than about 25 minutes and preferably within about18 to 20 minutes, sodium silicate and sodium sulfate also being fed tothe reaction within such times where the total of such materials is notalready present in the reaction medium. Further, where the objective isto produce materials better suited for such as the tire and paperindustries, longer commingling times are found to be more desirable.Especially in the case of tire pigment production, wherein it ispreferred to provide a reaction medium containing less than 50 percentof the calculated total quantity of sodium silicate and sodium sulfate,as for example 10 percent, it is found to be preferable that the totalof the aluminum sulfate and the remaining quantity of sodiumsilicate-sodium sulfate solution be commingle'd in the reaction mediumby delivering separated streams thereto over a period not less thanabout 25 minutes, preferably 35-40 minutes. Within these indications, itwill be appreciated, that rather precise correlations are necessary withother factors affecting pH of the various reaction media so that theprecipitation reaction takes place according to the more desirable pHconditions indicated hereinbefore.

Reference has been made heretofore in this specification toconcentrations of sodium silicate and sodium sulfate as well as thedesirable degree of dilution provided by the actual reaction medium. Itwill be appreciated, while bearing in mind that high dilution isdesirable in the production of the type of end product sought,(especially overall uniformity of particle character,) that dilution ofthe reactants as a practical matter may be accomplished by employingvery highly dilute stream that are delivered to a reaction mediumcontaining a suitable quantity of relatively concentrated sodium sulfatesolution. it also may be remarked that unnecessary dilution merelyintroduces a water removal problem and otherwise affects economics ofthe process. Thus, is specifying hereinafter the concentration ofaluminum sulfate, it will be understood that such is in relation to thetotal quantity of water which may be introduced into the process asgenerally taught and contemplated to be suitable as hereinbefore indicated, other conditions being taken into account. Accordingly, having inmind concentrations which are suitable in relation to the other suitableconditions herein discussed whereby the various products are obtainable,it has been found that the concentration of the aluminum sulfate streammay vary considerably, however, preferably as a practical matter, notless than about 0.1 and not more than about 3.5 lbs/gal. Morespecifically, and in relation to other conditions indicated to besuitable in connection with products for use in shoe soles and the like,aluminum vsulfate concentrations of about 1.2 to about 1.6, specificallyabout 1.4

lbs/gal. are particularly applicable. On the other hand, a more suitableconcentration relative to other suitable conditions for tirereinforcing, paper and the like, is from about 2.2 to 2.8 lbs/gal., moreparticularly about 2.5 lbs/gal.

In all instances, the quantity of aluminum sulfate actually fed to theprecipitation reaction is such as to provide a final slurry having a pHlevel consistent with the pH of the desired end product.

No special equipment is required in the processes herein described. Thereaction vessel itself should be equipped with heating means, forexample a steam jacket, in order to maintain the desired reactiontemperature; also, it should have adequate agitating means to produce astrong backflow on the body of liquid and thus avoid zones of highconcentration of the incoming reactants. It is desirable to bring thereactants together so as to produce an instantaneous reaction of allmaterial being fed to the fullest extent reasonably possible, as suchpromotes uniformity of the resulting products. Storage vessels equippedwith heating means are provided for the reactants, they being connectedto the reaction vessel thru lines fitted with flow control means. Thereaction vessel is equipped with an outlet line leading to a filterwhich may be of the rotary-string release type, where the precipitate iswater washed to remove sodium sulfate as a liquor, the latter liquorbeing sent to storage. A portion of this sulfate liquor is utilized insucceeding production as the source of the minimum amount of sodiumsulfate needed according to this invention. The filter cake beingthixotropic requires to be liquefied and for this purpose a tank isrequired equipped with a suitable beater. The mass is dried inconventional spray drying equipment.

The immediately following example illustrates detailed procedure andconditions which may suitably be followed in practicing the invention.

EXAMPLE 1 The reaction vessel is charged with 10 gals. of water and asodium silicate (Na O2.5 SiOfl-sodium sulfate solution of a silicateconcentration of 1.6 lbs/gal. and a sodium sulfate concentration of 5percent by weight of the silicate is delivered thereto at a rate of0.196 gpm (gallons per minute) for one minute. The temperature of theresulting reaction solution is established and maintained at F. Alum inconcentration of 2.6 lbs/gal. at a temperature of 160F is delivered tothe reaction volume, the agitator being first started, at a rate of0.066 gal/min. while simultaneously feeding the remaining calculatedquantity of the sodium silicatesodium sulfate solution at its rate of0.196 gpm. This solution being fed over a time of 38 minutes at whichtime it is discontinued. Alum flow is continued until the pH of thereaction mass is lowered to 5.9. A setting or digestion period of 15min. is observed and pH is again measured and readjusted to the 5.9value, following which it is delivered to the filter where it is washedwith water for recovery of sodium sulfate and to reduce its residualcontent to about 3 percent. The resulting cake,

.being solid (thixotropic), is delivered to a beater and fluidized afterwhich it is spray dryed at an outlet pigment temperature of about 220Fto a moisture content of 5 percent. The resulting dry pigment has a pHof 8.5 and the mass is composed of extremely fine particles relativelyfew of which are larger than 0.5 micron.

TABLE TABLE- Continued Example umber 1 2 3 4 Example number 11 12 13 1Volume of reaction, water/gallons 10 10 10 10 255 255 Silicate feedrate, including NazSO ga1s./ 5 0 '{fifj min 0. 196 0. 196 0. 196 0. 1964 4 3g 39 Initial silicate-sulfate feed. tlme/mlns-.. l 7. S 19. 5 31. 235 35 Silicate-sulfate addition, time/mins. 38 31. 2 19. 5 7. 8 z 5 1 5'i'ggfisi gillitcate congentiiratiionllibsltgaal .i- Lg 1.? 1. g l. 6 u78 (1'72 23 a concen In on n ca percen 5 Alum concentration, lbs. a1. 2.a 2.6 2.6 2. o giggg ggg gggg ig g 2 7 7 L 7 0 Concentration silicate inreactor before Starts lbs lgal a 18 a n 1 53 1 53 alum starts,1bs./gal0- 03 0. 20 0. 44 0.61 Alum a h' a 01 1 39 75 5o Alum rate, gal/min 0.066 0. 076 0. 102 0. 159 10 Reaction i EF 135 50 150 130 Reactiontemperature, F. 160 160 160 160 Alum feed temperatme o i 130 130 150 130Alum lead temperature, F 130 130 130 130 Final slurry DEL 0 0 a n 9Final Yr D 9 9 5r 9 9 Djgesfiml temperature 135 150 150 3 1 itmpermm-Digestion time- 15 15 15 1s Dlgesflml tulle 15 15 15 15 Pigment, pH s. o7. 3 9. 6 1n 1 Plgment 5 45 31 0 Rubber results tires (of! the road):

Rubber results, 8 501%8- Tear at 90 min/cold 730 660 615 585 IIHQBIV1500 ty 8 0 7 5 15 at t,, 390 42 340 350 Mimmum g 4 9 25-: 7 Abrasionat so min. cure 72.6 62. o 91. 2 96. 4 081W 2 9 2 Q Flexometer(Firestone) to min.. 263 215 267 2:2 swell 34 Scorch time. 19. 5 19. 017. 5 19. s

8 min.0lsen strflness- 36. 1 41. 0 41. 3 43. 2 Viscosi 78 70 74 8 H1111-NBC B-bIESlOIl 77 78 70 66 El tiafi gt o 55 550 49 5m Newspflnt Hardnessat min. cure 71 70 e9 e9 TAPPI brightness at 5% loading"... 64. 9 04. 664. 4 63. 9 Newsprint results:

TAPPI opacity at 5% loading.. 88. 6 87. 8 86. 8 86- 5 2O TAPPIbrightness at loading 64 6 6L 6 63. 6 a 9 Ink Pick fit5%1adin8 8 7 9TAPPI opacity at 4% loadl 87.3 87.4 as. s 87.9 Percent strike thrureduction at 5% Ink pickup at 4% loading 4 8 3'8 3 v 9 loadmg 8 0 4 6Percent strike thru reduction a 65. O 72. 4 57. 2 56. 2 Percentretention at 5%10ad1ng 5 o 3 1 Ferment retention at 4% l0ad1m7 51 2 50,0 41 5 48, 3

"' M TABLE- Continued IABLE- Continued 2 5 Example number 15 16 17 18Example number 5 6 7 8 Volume of reaction, Water/gallons 10 10 10 10Volume ofreactiomwater/gallons l0 5 1,800 1,800 123: feed rate includingNazso" O 196 0 196 0 196 0 196 Initial silicate-sulfate feed time 39.0 439. 0 4 ca a e a m 0 snicsts sniratc mannn, main rs o 35 o as 30 gig? glbs/L Salt concentration in silicate, percent 5 0.0 3. 0 7. 0 g g g g' g5 32;?" 4 0 4 2 5 lum starts lbs/gal 0. 71 0. 07 0. 71 0. 11 Aalumstarts, lbs/gal 0. 69 0.33 0.71 0.11 Afilmme mm 0 25 o 0 30 o 098 "6'i-"250 119 4 6 Reaction temperature, F 140 170 140 170 temp 135 Alum feedtern rature F 140 140 140 130 Alum feed temperature, F 130 160 3 5 Finalslurry fi 6 0 7 0 6 0 7 o g gg fifg fgg g gz 2 g Digestion temperature"170 140 170 Di t t 15 5 15 15 Digestion time 15 15 15 15 Pigment, pH 8.5 7. 3 7. 9

"Rubber Results, shoe soles:

Initial viscosity 34. 8 27. O 27. 1 M Minimum viscosity. 28. 5 24, 0 24.0

Maximum viscosity. 54. 6 52. 7 53. 7

Scorch time 3. 41 2. 92 2. 25- 4O 3min. sttiflgiiess. 4952 3663 466? m11. Hr 1'8 on assesses 1 .1 7 EXAMPLE i ggggi g g? $3313 The reactionvessel is charged with 9 gallons of water r1 pc ups. oaing Percentstrike thin reduction at 5% and a sodium s licate sodium sulfatesolution of a $111 loading es. s 45 cate concentration of 2.0 lbs/gal.and a sodium sulfate Percent retention at 5% loading 53. 1

res s mi uc" Example number Volume of reaction, water/gallons 1 Silicatefeed rate, including NMSOt, gals./m.in.- Initial silicate-sulfate feed,time/min Silicate-sulfate addition, time/min--. Silicate concentration,lbs/gal. Salt concentration in silicate, perceuL- Alum concentration,lbs/gal Concentration silicate in reactor before alum starts, lbs/gal.Alum rate, gal/min Reaction temperature, F Alum teed temperature, Finalslurry, pH Digestion temperature Digestion time Pigment, nH Rubberresults, shoe soles:

Initial viscosity Minimum v m y Maximum viscosity Scorch time 8 min.Olsen stiffness 8 min. NBS abrasion Newsprint results:

TAPPI brightness at 5% loading 65. 3 TAPPI opacity at 5% 1oadlng.....Ink pick up at 5% loading Percent strike thru reduction at 5% loadingPercent retention at 5% loading concentration of 2 percent to 6 percentby weight of the silicate is delivered thereto at a rate of 1162.6ml/min. The temperature of the resulting reaction solution isestablished and maintained at F. Alum in concentration of 3.0 lbs/gal.at a temperature of 160F 'is delivered to the reaction medium, theagitator being started first, at a rate of 0.09 to 0.11 gpm (gallons perminute) for 10 seconds or more prior to the start of the sodiumsilicate-sodium sulfate solution at which time the remaining calculatedquantity of the sodium silicats-sodium sulfate solution is started atits rate of 1 162.6 ml/min. After 25 minutes, the silicate solution isstopped if the slurry pH is above 8.0. The alum is continued until a pHof 7.8 8.0 is reached. If the pH is below 8.0, the silicate solution iscontinued until a pH of 8.0 is reached. A setting or digestion period of15 minutes is observed and pH is again measured and readjusted to the7.8 8.0 value, following which it is delivered to the filter where it iswashed with water for recovery of sodium sulfate and to reduce itsresidual content to about 3 percent. The resulting cake, being solid(thixotropic), is delivered to a beater and fluidized after which it isspray dried at an outlet pigment temperature of about 220F to a moisturecontent of percent. The resulting dry pigment has a pH of 9.5 and themass is composed of extremely fine particles relatively few of which arelarger than 0.5 micron.

Fine Paper Results TAPPl Brightness at 9 percent loading 89.5

TAPPl Opacity at 9 percent loading 87.8

The following materials, in the quantities indicated, describe astandard testing composition employed to test the exemplary productsherein in rubber for use in tires, more particularly heavy-duty tires ofthe off-the- 1 road type:

TEST RECIPE OFF ROAD TIRES PARTS BY WT.

Th e fo llowin g material s, iii sequintiassifieaaa, describe a standardtesting composition employed to test the exemplary products herein inrubber for use in shoe soles, heels, and the like:

5. ZEOLEX 23 (synthetic pigment material 7.0 produced according to U. S.patent 2,739,073 us by example 6 herein) 6. Pigment (products ofexamples l-5 and 70.0 7-l8 herein) 7. Stearic acid 1.0 8. Carbowax(Polyglycol 6000 4.0 molecular weight) 9. Phthalic anhydride .65 I0.NOBS (Special normal oxydiethylene 1.00 benzothiazole) 1 l. Captax(mercaptobenzothiazole) 0.80 12. DOTG (diorthotolylgunadine) 0.80 13.Octamine (diphenylamine and diiso- 1.0 butylamine) 14. Circo Light Oil(Naphthenic type oil) l5.0 15. Sulfur 2.8

"Efifiiffies b and 9 as presented above ar e illustrative of the bestresults obtainable following the teachings of U. S. Pat. No. 2,739,073.

In examples l-l 4 a sodium silicate of the weight ratio NEQOTZISs10;wag'em is eaietaasies 15, i6 and 19 indicate procedures andconditions wherein the silicate weight ratio is according to the formulaNa2O:3.3 SiOz. Examples 17 and 18 illustrate pro cedures and conditionswherein the silicate has the ratio of Na O:2.0 SiO2. In Examples 15 to18 the results obtainable are entirely similar to resultsobtained in theuse of the 2.5 ratio silicate cam'ed out according to this invention.

The invention may be practiced utilizing a wide range of silicates, moreparticularly within the range of about 1.516 3.S SiOI:NaQO by weight.

The test data, respecting initial, minimum and maximum viscosity andalso scorch time, was derived utilizing the Monsanto Oscillating-DiskRheometer.

What is claimed is:

1. Paper products containing papermaking fibers and filler materialsproduced according to the process of producing materials composed of theoxides of sodium, aluminum and silicon, wherein sodium silicate and 21aluminum sulfate are reacted in an aqueous medium following which theresulting precipitate is washed, filtered, dried and recovered in arelatively dry, finely divided state, and wherein the improvementcomprises supplying sodium sulfate to said reaction over its course inan amount equal to at least I percent by weight based on the weight ofsaid silicate, at least about 0.1 of which sulfate is provided in saidaqueous reaction medium from the inception of the reaction.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent No.3,7841442 Dated January 8, 1974 lnventofls) LoweII E. Hackbarth andJoseph T. Crockett It is certified that error appears in theabove-identified patent and that said Letters Patent are herebycorrected as shown below:

CoIumn I5 ingredient numbered 6 between lines 20 25z "quinoh'ne(SantofIex DD)" shouid be in Ieft coIumn and "0.5" onIy shouId be to theright of coIumn.

Column 15, between h'nes 35-40, ingredient numbered 1:

foIIomng "nondisc0I0ring" the word Iow shouId be inserted.

comma 16, first line:

insert f0] lowing "ZeoIex".

Signed and sealed this 6th day of August 1974.

(SEAL) Attest:

McCOY M. GIBSON, JR. C. MARSHALL DANN Attesting Officer Commissioner ofPatents F ORM Po-wso (IO-69) USCOMM-DC 60376-P69 fi Us GOVERNMENTPRINTING OFFICE I969 0-366-331

